This honestly shouldn't be a problem to you. As I say that, that doesn't mean the game is a breeze. Use cover and go slowly. Often use the "move forward" and then retreat method to trigger bad guys showing up. Although you may think at times that you can just run up to bad guys and pull the trigger without aiming, that will often get you killed. As I write this I still don't have the "complete a level without dying" achievement even though I beat this game on only the minor hazard (easy).
If you aren't concerned with the "get 50 kills with ____ weapon" achievements, try to pick the best ones up. This means you should ignore the six shooters and shotgun and sniper and focus more on the small but accurate pistols, specifically the laser pistol.
The game is long, I do warn you. However, it is warranted since there is nothing other than the single player in this game. This will take you some time. My best suggestion is to not play the game straight - you'll end up ignoring cover and becoming reckless, forcing you to replay certain levels and make the game longer than it needs to be.
Last tip. If you only intend to play through the game once, don't worry about such achievements as "say no to pot" and the shooting of the fire extinguishers. Do what I suggested in those guides specifically (go check them out!). Work towards the "get 50 kills with weapon ____" as you play through should probably be your major priority besides simply beating the game.